Septicemia Caused by Herbaspirillum huttiense Secondary to Pneumonia

Abstract

Dear Editor, Herbaspirillum species are non-fermenting gram-negative bacilli of the class Betaproteobacteria, found in the environment, including soil, groundwater, and drinking water distribution systems [1]. They are curved or sometimes helical in shape, strict aerobes, motile with polar flagella, and urease-, oxidase-, and catalase-positive [2]. These species are rarely associated with human infections but can cause bacteremia and sepsis in immunocompromised patients [3]. Human disease caused by Herbaspirillum species has been previously described in cystic fibrosis patients. Herbaspirillum has been reported to be an opportunistic pathogen in patients with cirrhosis and cancer as well as a cause of pneumonia in an immunocompetent farmer in the United States [4]. We report the first case of septicemia caused by Herbaspirillum huttiense in Korea. This study was approved by the Institutional Review Board for Human Research, Yonsei University, Severance Hospital (IRB No. 4-2018-0620) with waiver for informed consent. A 93-year-old male was admitted to the hospital with seizures and fever. Although the patient was of advanced age, he had no remarkable past medical history except for hypertension, for which he was on medication. The patient was suspected to have encephalitis, and vancomycin and ceftriaxone were administered to him immediately. Initial blood, sputum, and cerebrospinal fluid bacterial cultures showed no growth of pathogens. After a few days, dyspnea, O2 desaturation (85%), tachycardia, and profound hypotension were observed, and radiological examinations showed pneumonia. Staphylococcus aureus and a gramnegative bacillus were isolated in subsequent blood cultures. The colony morphology of the gram-negative bacillus on sheep blood agar was grayish, non-hemolytic, circular, smooth, and convex. It was identified as H. huttiense by matrix-associated laser desorption ionization-time of flight mass spectrometry (MALDITOF MS; MicroFlex LT, Bruker Daltonics GmbH, Leipzig, Germany) with an identification log score of 2.30, but as a member of the Burkholderia cepacia group by the VITEK 2 system (bioMérieux, Marcy l’Etoile, France). The strain produced acid using adonitol, L-arabitol, D-glucose, and D-mannitol as substrates and could utilize D-mannose and D-sorbitol as carbon sources. Moreover, the strain was positive for malonate, citrate, L-lactate, and succinate alkalinization, as well as beta-galactosidase, gammaglutamyl transferase, L-proline arylamidase, tyrosine arylamidase, and L-malate assimilation, based on the VITEK 2 gram-negative identification card. To confirm the bacterial species, 16S rRNA gene was sequenced with the following primer pairs, according to the CLSI guidelines: forward primer, 4F: 5 ́-TTG GAG AGT TTG ATC CTG GCT C-3 ́ and reverse primer, 534R: 5 ́-TAC CGC GGC TGC TGG CAC-3 ́ and forward primer 27F: 5 ́-AGA GTT